Phased array antennas are a commonly employed expedient for obtaining a prescribed antenna profile that may provide communication coverage over a defined surface area in space. For satellite communications, in particular, where coverage of the entire upper hemisphere is required, previously proposed arrays have involved multiple planar arrays configured as a tetrahedral arrangement or as a spherical or hemispherical dome. Exemplary illustrations of such hemispherical and spherical approaches are presented in the October 1981 issue of "Microwaves" and in a technical brief of the Aerospace Systems Division of Ball Brothers, entitled "Electrically Steerable Spherical Array, Executive Summary", October 1981.
Unfortunately, investigation has shown that a hemispherical array provides illumination of only one-half of the surface area at the horizon, while the entire surface area is illuminated at zenith. This results in an excess gain as the elevation angle increases, which is inherently inefficient. Tetrahedral arrays have similar problems at the intersections of the planes.